The BIMA cryocooler is a 3-stage Gifford-McMahon cryocooler developed at U.C. Berkeley to cool SIS (Superconductor-Insulator-Superconductor) mixers on radio telescopes. The cryocooler is basically a CTI model 1020 cold head with a third stage welded onto the end. Spheres of Er3Ni or HoCu2 (both obtained from Toshiba America Electronics) are used as the regenerator material in the third stage. The cooling capacity is roughly 50 mW at 4.2 K.

Papers describing the cryocooler:

• "A 4 K Gifford-McMahon Refrigerator for Radio Astronomy," R. Plambeck, N. Thatte, and P. Sykes, 1993, Proceedings of the 7th International Cryocoolers Conference (Air Force Philips Lab publication PL-CP-93-1001), p. 401. scanned pdf


• "Improved Seal for a 4 K Gifford-McMahon Cryocooler," R.L. Plambeck 1995, in Cryocoolers-8 (R.G. Ross, Jr., ed.), New York: Plenum, p. 795. pdf


• "Long Term Performance of 4 K Gifford-McMahon Refrigerators on the BIMA Array," R.L. Plambeck 1998, in 'Advances in Cryogenic Engineering,' vol 43 (P. Kittel, ed.), New York: Plenum, pp. 1815-1821. (presented at the Cryogenic Engineering Conference, Portland, Oregon, 1997 Jul) pdf

Drawings:

• 28-024A.pdf - overall dimensions


• 28-024B.pdf - 3rd stage cylinder


• 28-024D.pdf - 3rd stage heat station


• 28-024E.pdf - Bal-Seal clamp ring


• 28-024E1.pdf - Bal-Seal clamp ring detail


• 28-024E2.pdf - Bal-Seal clamp ring detail


• 28-024M.pdf - 3rd stage displacer construction


• 28-024J.pdf - 3rd stage displacer, older design


• 28-024C.pdf - modifications to 2nd stage displacer


• 28-024F.pdf - 3rd stage displacer linkage


• 28-024I.pdf - miscellaneous parts


• 28-024W.pdf - welding instructions


• 28-024G.pdf - seal insertion tool